The present invention relates generally to irrigation systems using drip irrigation tubes. The drip irrigation tubes can be set either on the surface or burried in the ground. Such drip irrigation tubes are disclosed in U.S. Pat. No. 3,830,067, and U.S. Pat. No. 3,698,195 and U.S. Application Ser. No. 488,827. In the past when installing such drip irrigation systems it has been necessary to use a valve which must be manually adjusted to provide the proper flow. Many drip irrigation tubes undergo a break in period after which their effective porosity changes and it is necessary to readjust the flow control valve.